How To: Create a Bed

The components of a bed

To create a bed you need to create and combine the following items:

• A fragment of the topography where the bed outcrops at the surface.

• A line at a specified angle representing the top surface of the bed.

• A line at a specified angle representing the bottom surface of the bed.

• A base line joining the top and bottom surfaces at the bottom of the section.

Make invisible and lock (make the pencil grey) all of the layers except that on which you wish to work. Make that layer the active layer. You need to be able to identify the surface nodes that represent contacts.

Bed contacts

Set Snap to Objects to ensure your bed contact will start at the contact node in the topography. Unset Snap to Grid so that you can draw a line at any angle. Determine the required dip of the bed from the original map (or your paper section). Zoom in as much as possible whilst still having the intended start and end points of the bed contact in the field of view.

Select the Freehand Tool and click on the topography contact node. Move the mouse to to the end point of the line, watching the status bar to ensure the line is at the correct angle. You may need to take the contact line below the base of the section and trim it back later using the Intersect tools. Also, it is unlikely that you will be able to obtain the correct angle exactly - a value to with half a degree of that required will probably be undetectable visually. If you want the line drawn to and exact angle, draw a long horizontal or vertical line (holding down the Ctrl key) and rotate it with the Transformation docker.

At this stage your drawing will be something like this:

Base Line

Draw a line connecting the bases of the two bed contacts.

Topography fragment

Select the Shape Tool and click on the topography. Click on the node at top of one of the contact lines and then click on the Break Curve button. Do the same for the other contact. Now click on the Arrange|Break Apart menu. Click off the selected objects to de-select them. Then click on the topography well away from the bed. Click the Cut button or use Ctrl+X or the Del key. You should be left with a complete outline of the bed made from four separate lines (possibly three lines).

Combine and Close the lines

Use the Pick Tool to select all four lines. Click the Arrange|Combine menu. With the Shape Tool select each pair of superimposed nodes and join them in turn. You may need to zoom in so that you can select only the required nodes. Select a colour and the bed should fill.

If not, check that all the lines are combined and superimposed nodes are joined.

Repeat this entire procedure for other beds and other layers.